Maintaining the integrity of the genome is essential to cell survival. To accomplish this vital task, major cell cycle events including chromosome replication, segregation, and proper timing of cytokinesis are exquisitely coordinated, temporally and spatially. Any defect that disturbs this coordination can be lethal. Although replication, segregation, and cell division have been extensively studied in bacteria, our understanding of how these processes are coordinated remains limited. Bacteria?s survival also depends on their ability to coordinate cell cycle progression with environmental fluctuations. In this project, we focus on the conserved chromosome replication initiator protein DnaA and its non-replicative functions. The long-term goal is to characterize the molecular functions of regulators that coordinate the progression of the cell cycle and thus represent potential drug targets. The overall objective of this project is to define the mechanisms used to temporally coordinate the onset of chromosome replication with the progression of the cell cycle using the bacterial model system Caulobacter crescentus. The central hypothesis is that DnaA controls the activity of key regulators involved in chromosome segregation and cell size determination. The focus of Aim 1 is to define how DnaA coordinates chromosome replication with the onset of segregation by characterizing the physical association of DnaA with the chromosomal locus the centromere over the cell cycle. The focus of Aim 2 is to define the molecular network that links DnaA?s activity to cell size regulation and its dependency on nutrient availability. Information garnered from this project will provide valuable insights into strategies used by bacteria to temporally and spatially coordinate the multiple mechanisms that are fundamental for the cell survival.